3x^2+8x=123

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Solution for 3x^2+8x=123 equation:


Simplifying
3x2 + 8x = 123

Reorder the terms:
8x + 3x2 = 123

Solving
8x + 3x2 = 123

Solving for variable 'x'.

Reorder the terms:
-123 + 8x + 3x2 = 123 + -123

Combine like terms: 123 + -123 = 0
-123 + 8x + 3x2 = 0

Begin completing the square.  Divide all terms by
3 the coefficient of the squared term: 

Divide each side by '3'.
-41 + 2.666666667x + x2 = 0

Move the constant term to the right:

Add '41' to each side of the equation.
-41 + 2.666666667x + 41 + x2 = 0 + 41

Reorder the terms:
-41 + 41 + 2.666666667x + x2 = 0 + 41

Combine like terms: -41 + 41 = 0
0 + 2.666666667x + x2 = 0 + 41
2.666666667x + x2 = 0 + 41

Combine like terms: 0 + 41 = 41
2.666666667x + x2 = 41

The x term is 2.666666667x.  Take half its coefficient (1.333333334).
Square it (1.777777780) and add it to both sides.

Add '1.777777780' to each side of the equation.
2.666666667x + 1.777777780 + x2 = 41 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667x + x2 = 41 + 1.777777780

Combine like terms: 41 + 1.777777780 = 42.77777778
1.777777780 + 2.666666667x + x2 = 42.77777778

Factor a perfect square on the left side:
(x + 1.333333334)(x + 1.333333334) = 42.77777778

Calculate the square root of the right side: 6.54047229

Break this problem into two subproblems by setting 
(x + 1.333333334) equal to 6.54047229 and -6.54047229.

Subproblem 1

x + 1.333333334 = 6.54047229 Simplifying x + 1.333333334 = 6.54047229 Reorder the terms: 1.333333334 + x = 6.54047229 Solving 1.333333334 + x = 6.54047229 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.333333334' to each side of the equation. 1.333333334 + -1.333333334 + x = 6.54047229 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = 6.54047229 + -1.333333334 x = 6.54047229 + -1.333333334 Combine like terms: 6.54047229 + -1.333333334 = 5.207138956 x = 5.207138956 Simplifying x = 5.207138956

Subproblem 2

x + 1.333333334 = -6.54047229 Simplifying x + 1.333333334 = -6.54047229 Reorder the terms: 1.333333334 + x = -6.54047229 Solving 1.333333334 + x = -6.54047229 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.333333334' to each side of the equation. 1.333333334 + -1.333333334 + x = -6.54047229 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = -6.54047229 + -1.333333334 x = -6.54047229 + -1.333333334 Combine like terms: -6.54047229 + -1.333333334 = -7.873805624 x = -7.873805624 Simplifying x = -7.873805624

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.207138956, -7.873805624}

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